Mystery of North American Black Wolves Solved

A very particular phenomenon is observed in the packs of the North American continent: the number of black wolves increases compared to that of the gray wolves when one moves along the Rocky Mountains, from the Canadian Arctic towards the national park of Yellowstone, United States.

The black wolf is non-existent or very rare almost everywhere in the world, but it is rather common in certain regions of North America, notably in Yellowstoneexplains in a press release Professor Tim Coulson of the Department of Biology at the University of Oxford.

To succeed in understanding this anomalyProfessor Coulson, his team and colleagues from Pennsylvania State University analyzed the genetic data of twelve North American wolf populations collected over 20 years.

Four wolves are playing in the snow.

Many wolves in the Druid Peak pack are black.

Photo: Yellowstone National Park/Daniel Stahler

Between dog and wolf

  • The coat color of wolves (Canis lupus) is determined by the CPD103 gene. Depending on which gene variant a wolf has, its coat can be black or gray.
  • The ancestral version of the gene determines a gray coat. A mutation that appeared in domestic dogs and then crossed with wolves determines a black color.
  • The dog-associated mutation was likely introduced to the North American wolf population in the past 7,250 years, when humans migrated across the Bering Strait with dogs carrying the gene.
  • Cubs inherit two copies of CPD103 (one from each parent), but inheriting one copy of the black variant is not enough to exhibit a dark coat.
  • Distemper (VMC) appeared in the 1730s from a bovine virus introduced into North America by settlers from Europe.

Genetic protection

Analysis of genetic data showed that black-mantled wolves had greater immunity to distemper, since they had antibodies that protected them against respiratory viruses.

Not surprisingly, black wolves were more likely to survive outbreaks of distemper than gray wolves.

In addition, the researchers also determined that the more black wolves there are in an area, the more that territory has been hit by distemper epidemics in the past.

A pack of a dozen wolves.

About half of Druid Peak’s pack is black.

Photo: Yellowstone National Park/Daniel Stahler

Selective couplings

The researchers also found that black and gray wolves were more likely to mate together in areas where distemper outbreaks are common. However, this competitive advantage disappears in disease-free areas.

We have found that wolves can signal their resistance to canine distemper virus by their coat color, which could allow individuals to identify mates capable of providing them with healthier offspring.said Peter Hudson, professor of biology at Pennsylvania State University

Fascinatingly, the disease protection gene came from domestic dogs that accompanied early humans to North America, and the disease virus appeared on the continent many thousands of years later, again at from dogsnotes Peter Hudson, professor of biology at the University of Pennsylvania.

According to the authors of this work published in the journal Science (New window) (in English), other animal species, including insects, amphibians, birds, and mammals, certainly show associations between color and disease resistance.

In addition, it is highly likely that the presence of a disease, and its frequency of occurrence, is an important factor influencing the color of a mating partner.

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